The present invention is in a method for using cleaning agent and more specifically relates to a method agent for cleaning apparatus used for the fabrication of reactive multiple-component mixtures containing isocyanate.
In the manufacture of fast-curing plastics or plastic foams based on polyurethane and polyisocyanurate, fabricating apparatus are used in which the reactive mixtures containing isocyanate, which are needed for the production of the end product, are fed to the molds through mixing heads. The mixing heads, which may be equipped with stirring mechanisms, tend to clog and must therefore be kept open by periodic flushing, usually after each batch, with suitable flushing agents. The hoppers, valves and pipelines ahead of the mixing heads also must be cleaned periodically with a flushing agent.
Heretofore solvents or solvent mixtures, in which the substances to be removed are soluble, have been used for cleaning. These solvents are normally chlorinated hydrocarbons such as dichloromethane, trichloroethylene, 1,1,1-trichloroethane, tetrachloroethylene, or carboxyl-group containing, highly volatile solvents such as acetone, methyl-ethyl-ketone, ethyl acetate, pentyl acetate, or mixtures thereof. Such agents are described in DE-OS 34 44 293.
One serious disadvantage of these solvents is that they are harmful to human health and to the environment, and due to their halogen content are expensive to remove, or are highly volatile and easily inflammable, so that special, complex apparatus are required to prevent explosions. For example, the flash point of ethyl acetate and methylethylketone is -4.degree. C., that of acetone less than -20.degree. C., and that of n-butylacetate, 25.degree. C.
The chlorinated hydrocarbons are toxic to the liver and nervous system, some are carcinogenic, and therefore are subject to special use and labeling regulations. Furthermore, these substances are poorly biodegradable in the soil.
DE-OS 35 17 170 discloses a cleaning agent which contains nonaromatic, high-boiling hydrocarbons and alkylated aromatic compounds of 8 to 18 carbon atoms. Such compositions also have sufficiently high flash points. However, such compositions have proven ineffective for use in apparatus for processing reactive multiple-component systems containing isocyanate.
An aqueous emulsion of a polyvalent alcohol with an oil-in-water emulsifier has been proposed in German Federal Patent 26 05 984. A serious disadvantage of this agent is that even if only minimal amounts of it remain in the fabricating apparatus, which can rarely be prevented, it can chemically react with the isocyanate component and form a residue resulting in problems in the apparatus. Furthermore, this agent can be used only for easily dispersible low viscosity contaminants.
It is an object of the present invention to obtain a noncarcinogenic cleaning agent which has good cleaning properties but which is difficultly inflammable especially for the cleaning of apparatus for the fabrication of reactive multiple-component mixtures containing isocyanate. It is a further object that the cleaning agent be safe to use and be readily disposable. The agent must completely dissolve or disperse the reactive components--the so-called "adducts"--as well as the products of the incipient reaction which are not yet highly crosslinked, without the need for using elevated shearing forces.